Duo dial generally refers to a “doctor's watch”, with a large subdial for the seconds hand. It can also be used for any watch with two dials, including dual movement dual timezone watches.

Doctors frequently use wrist watches as a timer when taking a patient's pulse. Although special-purpose pulsometer chronographs might be better suited for the task, many doctors prefer using the seconds hand instead. Before the introduction of central seconds, doctors found it difficult to precisely count seconds using a subdial. Therefore, companies like Hamilton, Elgin, and Rolex created so-called “duo-dial” watches with a seconds hand as large as the minutes hand. This subdial was usually placed below the regular hour and minutes dial in a rectangular case. This became known as a doctor's watch or duo dial watch.

In 1960, Nappey introduced the Jumelles Times watch with two movements side by side on the same dial for dual timezone use. Later models, including the Ardath Long Distance separated these dials, giving rise to the use of the duo dial term. This came to a head with Chopard who explicitly named their dual movement watch line Duo Dial. Other companies used the term, double dial or twin for these watches.